Fluid pressure control



M y 1953 J. F. SHANNON 2,637,342

FLUID PRESSURE CONTROL Filed Oct. 22. 1948 3 Sheets-Sheet 1 INVENTOR.

- JACK F. SHANNON FIG. 3

A ORNEY May 1953 J. F. SHANNON 2,637,342

FLUID PRESSURE CONTROL Filed Oct. 22. 1948 3 Sheets-Sheet 2 AIR SUPPLY FIG. 6

/ ZHAND AIR SUPPLY INVENTOR.

"AUTO JACK F. SHANNON 427M NEY I May 5, 1953 J. F. SHANNON 2,637,342

FLUID PRESSURE CONTROL Filed Oct. 22, 1948 5 Sheets-Sheet 3 AIR SUPPLY Q 49 48 AIR SUPPLY INVENTOR.

JACK F. SHANNON FIG. IO

BY 1 v W 5 agents.

Patented May 5, 1953 siren FLUID PRESSURE CONTROL Application October 22, 1948, Serial No. 56,001

9 Claims.

This invention relates to controlsystems operable automatically or manually to maintain substantially constant any desired electrical, thermal, chemical, physical or other variable condition through the control oi? a corrective agent or More particularly, my invention relates to control systems wherein a fluid pressure is utilized as the motive power for actuating devices to control the rate of application of corrective agents.

It is frequently necessary that a system be provided for regulating the supply of an agent effecting a condition, and the system should be operable either automatically in response to the condition for maintaining it at a desired constant value or manually for varying the condition as desired. The supply of the agent may be controlled by device which is operated by fluid delivered at a pressure regulated by the system. When the system is switched from automatic'to hand control or vice versa, the pressure supplied to the device immediately after the switch-over should be the same as the pressure supplied before the switch was made, otherwise an operation of the device may be obtained to vary the agent so as to upset the Whole system. It is therefore desirable that means be provided for regulating the pressure that would be supplied as well" as indicating both the supply and the control pressures.

An object of my invention is to provide an improved system for controlling a condition. Another object is to provide a system that may be adjusted for operation either automatically or manually to control a condition. Still another object is to provide an improved system in which a valve nicchanisni is selectively operative for supplying pressur fluid from automaticor manual control means to a regulating device, and separate gages are provided for indicating the supply and control pressures, the supply pressure gage indicating the pressure available at the control meansnot in control, and the control pressure gage indicating the pressure received by the regulating device. Other objects will appear in the course of the following description.

In the accompanying drawings there are shown for purposes of illustration two forms which my invention may assume in practice.

In these drawings:

Fig. 1 is a front elevational view of control apparatus einbodiedin my improved system.

Fig. 2 is a side elevational view of the apparatus shown in Fig. 1.

Fig. 3 is an enlarged vertical sectional View taken on the plane of the line 3-3 of Fig. 1.

Figs. 4 and5 are vertical sections taken on the planes of the lines l--4 and 5-& ofFig. 3.

Fig. 6 is a schematic diagram of my improved control system adjusted for automatic operation.

Fig. '7 is a schematic diagram like that of Fig. 6 but showing the system adjusted for hand operation.

Fig. 8 is a side elevational view like that. of Fig. 2 but showing apparatus for another form of my invention.

Figs. 9 and 10 are schematic diagrams showing the control systemsfor the apparatus of Fig. 8 adjusted for automatic and hand control.

Referring to the drawings, and more particularly to Figs. 6 and 7, it will be noted that my improved control system has been shown regulating the supply of pressure to a diaphragm actuated valve l for controlling the now of fluid through a conduit 2 to a container 3 so as to either maintain a condition therein at apredetermined value or cause the condition to vary as desired. A conduit 5 communicates with thediaphragm G of the valve I and is adapted to be connected by a valve l selectively to fluid supply conduits 8 and 9. The valve I used in the system as shown is adapted to open on an increase in the pressure supplied to the diaphragm 6. A standardizing relay, generally designated ill determines the pressure in the supply conduit 8, and a manually adjustableregulator [2 determines the pressure supplied from a source it to the supply conduitfi. With the valve 1 in the position shown in Fig. 6, the conduit 55 discharges pressure fluid through a groove I lintthe valve to the conduit 5, and the relay ill operates to regulate the pressure supplied to the conduit 8 in response to changes in the condition within the container.

The relay this like that disclosed in the Gorrie patent Re. 21,804 and comprises chambers l5, l6, ii and. N3, the chamberslfi, it being separated by a flexible partition l9, and the chambers ll, 18 being. separated by a flexible partition 2t. An elongated member M is connected to the partitions 19, 29 and acts on a'pivoted beam 22 for controllingthe positions of intake and discharge valves 26 and 25. An adjustable'spring 26 is connected to the member 2! and urges it away from the beam 22 to permit the latter to move in a directionfor unseating the discharge valve 25. Communicating with the chamber it is a conduit 28 which is connected with a pressure supply 29 andwith the atmosphere under the control of a pilot valve 30. A pressure responsive device 32, such as a Bourdon tube, is operatively connected to the pilot valve'and is subjected to a pressure proportional to the condition by an element 33 which is sensitive to changes in the condition.

The condition to be controlled may be the temperature within the container 3, in which case the fluid supplied by the conduit 2 may be a heating fluid, such as steam. Instead of making the system responsive to temperature it could as well be made responsive to the pressure in the container, or to any other variable that it may be desired to control. The operation of the pilot valve is such as to vary the pressure in the conduit 28 in inverse proportion to changes in the condition. If the valve I had been designed to close on an increase in the pressure supplied thereto then the pilot valve would be connected to vary the pressure in conduit 28 in direct proportion to changes in the condition. The pilot valve 30 is disclosed in the Johnson Patent 2,054,464 and need not be described in detail herein.

The chamber l6 of the relay is vented to'atmosphere, and the chambers I1 and I8 are connected in communication through a restricting valve 34 and a conduit 35. A conduit 36 opens into the chamber l1 and is adapted to be connected through a groove 31 in the valve "I to a conduit 38 branching from the supply conduit 9.

The valve I, as shown in Fig. 3 is rotatably received within a valve housing 40 which is attached, as by screws M, to a control panel 42.

A reduced valve portion 43 projects through the panel and has attached thereto an operating handle 44 having a pointer 45 which cooperates with marks 48 (see Fig. 1) for indicating whether the connected by the groove 48 to the gage 50, the

other conduit is connected by the groove I 4 to the diaphragm 6 and the gage 5|.

I When the valve I is in position for automatic control, as shown in Fig. 6, the groove l4 connects the conduits 5 and 8v for supplying a pressure determined by the relay ID to the diaphragm 8, and the age 5I indicates this pressure. The

groove 48 connects the conduit 9 to the conduit 49 for indicating on the gage 50 the pressure available at the discharge side of the manually adjustable regulator l2, and the groove 37 is moved to a position for breaking the connection between the conduits 36 and 38. If the pressure supplied by the conduit 28 to the chamber I5 is equal to the tension of thespring 26, and the pressures in the chambers I1 and I8 are equal, then the relay I0 is balanced, and the pressure in the chamber I8 is supplied to the diaphragm 6 for holding the valve I in somepartially open position. Any increase in the value of the condition will result in an operation of the pilot valve 30 to reduce the pressure supplied through the conduit 28 to the chamber I5. This will unbalance the relay so as to open the valve 25 andvent pressure from the chamber I8, thereby reducing the pressure supplied to the diaphragm 6 and effecting a closing movement of the valve I to reduce the flow of fluid to the container 3. The reduction of pressure in chamber I8 tends to rebalance the relay I0, but the pressure differential between chambers I1 and I8 results in a restricted flow of fluid from the chamber IT to the chamber I8 and the unbalance of the relay is maintained aslong as the pressure supplied to chamber I5 exerts a force less than that of the spring 26. A progressive reduction of the pressure supplied to the diaphram 6 therefore takes place to reduce the flow of fluid to the container 3 until the condition returns to the desired value and effects an increase of the pressure in the chamber I5 to balance the spring. If the condition drops below the desired value, the pilot valve is positioned to increase the pressure supplied to the chamber [5 until it exerts a force greater than that of the spring. The relay is then unbalanced to open the valve 24 and increase the pressure supplied to the diaphragm 6 for opening the valve I. The pressure in the relay chamber I8 continues to increase as long as the condition remains below the desired value.

If it is desired to regulate the pressure supplied to the diaphragm 5 by hand, the valve 7 is moved from the position of Fig. 6 to the position of Fig. 7. Before doing this, however, the device I2 is adjusted until the pressure at its discharge side, as indicated by the gage 50, is equal to the pressure supplied to the diaphragm from the relay III. This prevents a sudden change in the supply of fluid to the container when the system is first put onto manual control. With the valve in the position of Fig. 7, the manually adjusted pressure is supplied both to the diaphragm 5 and to the chamber I! of the relay Ill. Since this pressure is equal to the pressure that was supplied from chamber I8 before the switch-over was made, then the relay remains balanced, and the pressure in the chamber I8 is applied to the gage 50 through the conduit 8. the valve groove 48, and the conduit 49 to indicate a value equal to the value in dicated by the gage 5|. If the device I2 is now adjusted to vary the pressure supplied to the diaphragm 6, the same pressure variation takes place in chamber I 1 of the relay and effects operation of the latter to vary the pressure in the chamber I8 by an equal amount. Assuming that the pressure change on the diaphragm 6 produces no change in the temperature within tank 3, then the pressure on the diaphragm, as indicated by gage 5|, and the pressure in chamber I3 of the relay, as indicated by gage 50, will be equal. Any change in the diaphragm pressure by adjustment of the device I2 will be accompanied by an equal change in pressure within the chamber I8 as long as the temperature within the tank remains constant. An opening of the valve I by an increase in diaphragm pressure effects in time, however, an increase in the temperature and an operation of the pilot valve 30 to reduce the pressure in the chamber I5 of the relay. The pressure drop in this chamber unbalances the relay to reduce the pressure in chamber I 8 by an amount equal to the drop in chamber I5. There is then a difference between the pressures in chamber I1 and I8 and a restricted flow of fluid takes place between them, but this flow has no eflect on the pressure in chamber I! because the pressure is maintained therein at the value determined by the adjustment of the device I2. It also has no effect on the pressure in chamber I8, this pressure remaining at a value equal to the pressure in chamber I? reduced by an amount equal to the drop in pressure within chamber I5. The gages 50 and 5| now indicate values differing from each other by an amount proportional to the change in the temperature from the value that is maintained by the relay I 0 when on automatic control. As the temperature increases, the pointer of gage 50 drops below that of gage 5| by a proportionate amount, and a drop in the temperature below that which would be maintained automatically results in an increase in the readin-hand control position; the groove .the conduits 5, il'while thelgroove 53 connects the conduits '3; 49. :These. connections l are the same 1 In place of the conduit=t5-oonnecting the chambers El and H3 in the first form-of. the invention, there is pronected" to the'conduit 52.

ing: or gage: :over :thatigofigage 51 :bY WD 'OD :tionate 2 amount.

llfzthe operatorswishestto return the: system. to automatic control without any immediate change am the fluid supplied to thecontainer; he regulates :the devic :12 until. the readingsiof theagages Ell 'andEI' are equal. 50 is 'below' that or gage t l the operator knows that the temperatureris above the valueat'ivhich When the reading of thegage the relay ill-would be balanced; so :he adjusts the device I 2 to reduce-the pressure-on the diaphragm '6 for effectingmovementof the valve ltoward its closed position. If. the page 55! reads above l 5 l he changes the adjustment. of the deviceas to increase the pressure on the diaphragm li. ti -hen the readings ofthe gages are equal; the pressure supplied from the: pilot valve to the chamber l5 :balances the spring 25 :andthe pressures in the chambers Hand 18 are equal. The valve 'imay then be moved to the. automatic control position :without' changing theposition of the valve l Figs. 9 and 10 show schematically anarrange mentiof apparatus which is a little more than that described-abovean'd which performs the same functions. lnvthis arrangementthe relay I. and the device-lbdeterimine thepressure supplied to the conduits ligand 9 in the manner described above. The'valve'l is provided-however, with only the twogrooves it and 48,. the'groove I4 -connecting the conduits 5, l3 and the groove l il connecting the. conduits Sp i in the automatic control position of the-valve. When the valve it connects as in the first form of-the invention.

The operationof this form of the controlsystem Hr .is'the sameasthatof the'firstlform iniboth the automatic and hand control positions.

While there are 'described in'this application two forms which' my invention may assume in practice, it will be understood that the invention may be modified and embodied in various other forms without departing'irom its spi'ritor the scope of the appended claims.

What I claim as new and desire to secure by Letters Patent of the United States, is:

1. A system for controlling a condition comp-rising, in combination, pressure responsive means for determining the condition, means operating in response to changes in the condition from a predetermined value for establishing a first pressure varying in value in one direction or the other dependent upon the direction of change in the condition, manually adjustable means for establishing a second pressure at any desired value, means for subjecting said pressure responsive means selectively to said first and second pressures, means including said selective means for changing the operation of said operating means onl when said second pressure is subjected on said pressure responsive means so as to produce a third pressure varying directly with changes in the condition and-with said second :pressure, at

:pressuregage for indicating the-pressure supplied to said-pressure. responsive means" and a second pressure gage operative to indicate said second pressure when saidfirsti pressure is supplied to said pressure responsive 'means and to indicate saidthircl pressure-when said second pressure is supplied to said pressure responsive means.

-2...A system for controlling'a condition comprising, in. combination, pressure responsive valve means for regulating the flow of fluid determining the condition-"means includingua relay operating-to establish a first pressure varying in value in: response-to changes in the condition from a. predetermined value,wmanually:- adjust- =able n'ieans for establishing a second pressure at :any' desired value,1=a manually adjustable valve for subjecting said, pressure responsive valve .meansselectively to said first .and second pressures, meansrincluding said "manually adjustable valve for subjecting only the second pressureon the meanginoludinga relay establishing'said first pressurelsaid relayioperating when subjected to said-second pressure to establish a third pres- "sure: proportional to the valueofsaid' condition and tosaidsecond pressure, a pressuregagelior indicating the value of-' the pressure supplied to valve means.

4. A system for controllinga condition comprising, in combinations relay' having two pairs 'of chambers, the chambers of-each pair separated by a flexible partition, meansoperatively connecting'said partitions, supply and discharge valves regulating fluid flow relative to a chamber of one of said pairs under the control of said'connecting means; means for connecting the chambers of said one of said pairs in restricted communication, means for subjecting achamber of the other of said pairs to a pressure varying'with changes in thecondition; manually adjustable means for establishing a pressure at any desired value, pressure responsivemeansl for determining the condition, valve meansfor subjecting said pressure responsive means selectively to the pressure in the chamber relative to which flow is regulated by said supply and discharge valves and to the pressure established by said manually adjustable means, and means for subjecting the chamber opposite the one relative to which fluid flow is regulated to the pressure established by said manually adjustable means when said pressure responsive means is subjected to the same pressure.

5. The system of claim 4 including a pressure gage subjected continuously to the pressure supplied to said pressure responsive means, a second pressure gage, and means for subjecting said second pressure gage to the pressure established by said manually adjustable means when said pressure responsive means is subjected to the pressure in the chamber relative to which flow is regulated and to the pressure in the chamber relative to which fiow is regulated when said pressure responsive means is subjected to the pressure established by said manually adjustable means.

6. A system for controlling a condition comprising, in combination, a pressure chamber having a flexible wall, means providing a pair of pressure chambers separated by a common flexible wall, means connecting said walls together for simultaneous movement, a restricted connection between said pair of chambers, supply and discharge valves regulating fluid flow relative to one of said pair of chambers under the control of said connecting means, means for subjecting said first mentioned chamber to a pressure varying with changes in the condition, manually adjustable means for establishing a pressure at any desired value, pressure responsive means for determining the condition, adjustable valve means for subjecting said pressure responsive means selectively to the pressure in the one of said pair of chambers relative to which flow'is regulated by said supply and discharge valves and to the pressure established by said manually adjustable means, and means for subjecting the other of said pair of chambers to the pressure established by said manually adjustable means when said pressure responsive means is subjected to the same pressure.

I. A system for controlling a condition comprising, in combination, a pressure chamber having a flexible wall, means providing a pair of pressure chambers separated by a common flexible wall, means connecting said walls together for simultaneous movement, supply and discharge valves regulating fluid fiow relative to one of said pair of chambers under the control of said connecting means, means for subjecting said first mentioned chamber to a pressure varying with changes in the condition, manually adjustable means for establishing a pressure at any desired value, pressure responsive means for determining the condition, adjustable valve means for subjecting said pressure responsive means selectively to the pressure in the one of said pair of chambers relative to which flow is regulated by said supply and discharge valves and to the pressure established by said manually adjustable means, means controlled by said adjustable valve means and adapted to connect said pair of chambers in restricted communication when said adjustable valve means is in a position to subject said pressure responsive means to the pressure in said one of said pair of chambers, and means controlled by said adjustable valve means and adapted to subject the other one of said pair of chambers to 8 the pressure established by said'manually adjustable means when said adjustable valve means is in a position to subject said pressure responsive means to the same pressure.

8. The system of claim 7 including a pressure gage subjected to the pressure supplied said pressure responsive means, a second pressure gage, means for subjecting said second pressure gage to the pressure established by said manually adjustable means when said pressure responsive means is subjected to the pressure in one of said pair of chambers, and means for subjecting said second pressure gage to the pressure in said one of said pair of chambers when said pressure responsive means is subjected to the pressure established by said manually adjustable means.

9. A system for controlling a condition comprising, fiuid pressure responsive valve means for controlling an agent of the condition, means establishing a first fluid pressure representative of the condition, means sensitive to the first fluid pressure establishing a control fluid pressure representative of a deviation in the first fluid pressure from a desired value, manually adjustable means for establishing a second fluid pressure at a desired value, manually operated valve means with ports subjecting the fluid pressure responsive valve means selectively to the second fluid pressure and the control fluid pressure, valve ports in said manually operated valve means for establishing the second fluid pressure in the means sensitive to the first fluid pressure so that said sensitive means will produce an output fluid pressure varying directly with the first and second fluid pressures, a pressure gage for indicating the pressure supplied to the fluid pressure responsive valve, and a second pressure gage operative to indicate the second pressure when the control pressure is supplied to the fluid pressure responsive valve and to indicate the output pressure when the second pressure is supplied to the fluid pressure responsive valve.

JACK F. SHANNON.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date Re. 21,804 Gorrie May 20, 1941 2,202,485 Fitch May 28, 1940 2,369,887 Eckman Feb. 20, 1945 2,476,104 Mason July 12, 1949 FOREIGN PATENTS Number Country Date 458,823 Great Britain Dec. 28, 1936 

